Devices may be used, for example, in conjunction with tanks or pressure accumulator systems of vehicles in order to prevent overfilling of individual pressure accumulator vessels with fuel during a replenishing or filling operation. Various arrangements of pressure accumulator vessels and valves, and methods for the operation thereof, are known for this purpose.
Automotive pressure tank systems are currently checked prior to the refueling by a fuel-dispensing device of a filling station in respect of pressure level and tightness and are then correspondingly filled. Pressures of up to 10 bar in liquid gas systems, 200 to 300 bar in natural gas systems and 200 to 700 bar in hydrogen systems are customary as the filling pressure.
For hydrogen-operated vehicles, 350 and 700 bar are currently provided at filling stations. The different pressure levels of the pressure systems in vehicles are produced by tank necks of differing length. The length of the tank necks is designed in such a manner that a vehicle equipped for 350 bar cannot be replenished at a 700 bar filling station, but may be conversely. Tank systems of 700 bar are configured up to 875 bar in order not to be damaged due to thermally induced positive pressure or due to pressure surges (especially at the beginning of the replenishing operation). Several manufacturers arrange the tank and valves in such a manner that the filling line is connected directly into a valve block or is connected in parallel or in series into a plurality of valve blocks and the gas flows first through the valve blocks into the accumulator or the accumulators. Time and again in this case valves, valve seats and seals are damaged or the individual components in the valve block are caused to vibrate.
For motor vehicles operated with natural gas, there is currently a multiplicity of different refueling connections which are dependent on the type of motor vehicle (passenger vehicle, bus, lorry) and the country. (For example, ACME, bayonet or dish connection). A standard euro nozzle for Europe is planned.
Due to the relatively small ranges of vehicles operated purely by gas, an increase in the pressure level in Europe is being considered in the case of filling pressures for compressed natural gas (CNG) and mixed gas (for example, CNG and H2). This would mean that, in addition to the currently customary 200 bar tank systems, in the future, 248 or possibly 300 bar CNG systems and fuel-dispensing devices would be provided at filling stations. In the United States, the permissible operating pressure for CNG systems is 248 bar.
When refueling with natural gas, however, even in Europe, a pressure level of, for example, 260 bar in a 200 bar CNG tank system in a motor vehicle may be reached, since, at the beginning of refueling, there is a pressure surge for determining leaks and the current pressure level in the accumulator system. Moreover, the pressure accumulator vessel in the vehicle may therefore be filled up to a maximum pressure of the fuel-dispensing device (260 to 265 bar in the case of CNG) by refueling starts being repeated a number of times. This means a 30% exceeding of the permissible operating pressure of 200 bar. In order to avoid a safety risk, tank systems of motor vehicles already have to be configured now for 265 bar.
Filling stations have differently functioning or non-functioning monitoring systems for monitoring leakage and pressure and for switching off the fuelling operation. Fuel-dispensing devices at filling stations have customarily indicated the refueling quantity, but often not any pressure, for CNG.
U.S. Pat. No. 5,474,104 A discloses a tank cut-off valve construction which permits rapid, effective and reliable refueling of vehicles driven by CNG. The tank shut-off valve construction also permits expansion of the vehicle fuel system before maintenance and servicing of the vehicle. The tank cut-off valve construction has a receptacle which is suitable for fitting to a fuel-dispensing device of a filling station, and has a valve body with first and second gas flow passages. The corresponding first ends of the first and second gas flow passages are connected to the receptacle while the corresponding second ends of the first and second gas flow passages are connected to a gas accumulator vessel via a fuel supply line. The cut-off valve is positioned in the first gas flow passage of the valve body and is normally prestressed into a closed position in order to prevent gas flow through the first gas flow passage. The cut-off valve opens under pressure in response to a fuel flow by permitting gas flow to the fuel accumulator vessel.
A preferred embodiment of the tank cut-off valve construction disclosed in U.S. Pat. No. 5,474,104A furthermore has a bypass valve in the second gas flow passage in the valve body. The bypass valve is normally located in a closed position in which it blocks gas flow through the second gas flow passage. If maintenance or replacement of one or more parts of the construction is required, the bypass valve may be opened in order to permit gas flow back from the gas accumulator vessel through the receptacle, so as to empty the fuel system of a vehicle prior to maintenance. The receptacle may also have a filter in order to remove particles from the fuel. Due to the positioning of the cut-off valve within the valve body, the receptacle is not under pressure and may easily be removed for maintenance or replacement of the filter. The tank shut-off valve construction, however, lacks any device whatsoever for limiting the pressure in the pressure accumulator system.
European Patent Publication No. EP 1 561 991 B1 discloses a receiving element of a rapid-action coupling and a rapid-action coupling for the releasable connection of two pressurized fluid lines, and a system for filling car vessels with pressurized gas, the system comprising such a receiving element. Within this context, European Patent Publication No. EP 1 561 991 B1 discloses a rapid-action coupling for the releasable connection of two lines through which a pressurized fluid flows, the coupling comprising a plug-in element and a receiving element which are suitable for plugging axially one into the other. The plug-in element is equipped with a seal which is arranged in a receptacle which is incorporated in the inner surface of the body of the element, while the receiving element is provided with a closure valve. The valve is opened by a reaction force exerted by the seal of the plug-in element, the force resulting from the valve being supported on the seal as a consequence of the plug-in element and the receiving element intermeshing. The receiving element is therefore open by the valve being displaced only on account of the interaction between the valve and the seal of a plug-in element.
The intermeshing of the plug-in element and the receiving element does not result in the valve being displaced in the opening direction in the absence of the seal in the receptacle of the plug-in element. In particular, a rapid-action-coupling receiving element which belongs to such a coupling, and a rapid-action-coupling receiving element which is provided with a closure valve are disclosed. The valve is opened by a reaction force exerted by a seal arranged in an inner receiving space of the body of a coupling plug-in element which is suitable for being plugged into the receiving element. The force results from support of an outer circumferential slope or a transition zone between the end surface and a radial outer surface of the valve as a result of the plug-in element and the receiving element intermeshing.
European Patent Publication No. EP 2 122 222 B1 discloses a receiving or plug-in element of a coupling which serves for the releasable connection of pressurized lines through which a fluid flows, each connecting piece having a constant cross section over the entire length thereof.
European Patent Publication No. EP 1 561 991 B1 and European Patent Publication No. EP 2 122 222 B1 are representative of a number of known devices and technical solutions for the problem of reliable mechanical coding device between a fuel-dispensing device (e.g., fuel nozzle) of the filling station and tank neck of the motor vehicle. Problems, such as a small dead volume of the coupling, and embodiments of the frequently integrated nonreturn valves are also disclosed.
The solutions known in the prior art, however, lack any reliable devices for limiting the pressure in a tank system.
In order to reduce the multiplicity of tank necks and connections to fuel-dispensing devices of filling stations and to increase the operating reliability, a tank neck unit which is usable not only for different geographical regions but also limits the filling pressure in accordance with the permissible operating pressure of a tank system is proposed.
In the publications hereinabove mentioned, it is desirable for a permissible operating pressure of a pressure accumulator vessel or of a tank system to be reliably maintained over the course of a filling operation and thus to ensure maximum operating reliability. The filling operation is intended to be able to be carried out as rapidly as possible and with only low energy losses. Wear to valve components is intended to be kept low and damage to pressure accumulator vessels and pressure lines is intended to be prevented.
It is currently prohibited from replenishing at filling stations, the refueling pressure (nozzle pressure) of which exceeds the maximum working pressure of the pressure accumulator vessels installed in a vehicle.